ASIC needs for “observational cosmology”

Gary S. Varner University of Hawai’i

HEPIC 2013 LBNL

May 30th, 2013

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What’s in & out • Very broad topic; minimize overlap with 2

following talks

• Focus on UHE ν, CR detection in Radio

• To better clarify needs: – State of the art – Current developments – Future (anticipated) needs

• WFS in TeV gamma (CTA) [DRS, SAM, TARGET]

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Neutrinos: The only known messengers at PeV energies and above

• Photons lost above 30 TeV: pair production on IR & µwave background

• Charged particles: scattered by B-fields or GZK process at all energies

• Sources extend to 109 TeV ! • => Study of the highest

energy processes and particles throughout the universe requires PeV-ZeV neutrino detectors

• To guarantee EeV neutrino detection, design for the GZK neutrino flux

Region not observable In photons or Charged particles

Courtesy: Peter Gorham [U. Hawaii]

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Why Radio?? (Ultra-)High Energy Physics of Cosmic rays & Neutrinos

• Neither origin nor acceleration mechanism known for cosmic rays above 1019 eV

• A paradox: – No nearby sources observed – distant sources excluded due to

process below

• Neutrinos at 1017-19 eV

required by standard-model physics

galactic

extragalactic

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Radio Observation in dense media

1960’s: Askaryan predicted that the resultant compact cascade shower (1962 JETP 14, 144; 1965 JETP 21, 658): • would develop a local, relativistic net negative charge excess • would be coherent (Prf ~ E2) for radio frequencies • for high energy interactions, well above thermal noise:

• detectable at a distance (via antennas) • polarized – can tell where on the Cherenkov cone

neutrino Cascade: ~10m length

air

solid

RF Cherenkov

In the last decade or so… radio detection techniques finally flourishing

1. Radio Constraints on UHE neutrinos 2. ANtarctic Impulsive Transient Antenna (ANITA) 3. Serendipitous observation of UHE CR 4. Tera-ton Initiatives (ARA, ARIANNA, …)

Won’t cover low E CR, other radio, Atmospheric Molecular Bremsstrahlung

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Detector Energy Scales – the tonne

(total weight 7,000 tons, but sensitive elements much less)

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Detector Energy Scales – the kT

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Detector Energy Scales – the MT

Pushing bounds of civil

construction

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Detector Energy Scales – the GT

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Detector Energy Scales – the TeraTonne

IceCube ~200M$

Simply scaling up??

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Initial Round of Experiments • PRL 93:041101 (2004) limits published

Radio Ice Experiment (RICE) @ South Pole

Greenland Ice

• PRD 69:0133008 (2004) • Astropart.Phys.20:195 (2003)

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Design for cosmogenic ν flux discovery

• Huge Volume of solid, RF-transparent medium: Antarctic Ice Sheet

• Broadband antennas, low noise amplifiers and high-speed digitizers to observe them

• A high vantage point, but not too high nor too far away

• First realization: ANITA (balloon altitude)

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ANITA concept

Ice RF clarity: ~1.2km(!) attenuation length

Effective “telescope” aperture: • ~250 km3 sr @ 1018 eV • ~104 @ km3 sr 1019 eV (compare to ~1 km3 at lower E)

~4km deep ice!

Typical balloon field of regard

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Flight Payload Design

• Quad-ridged horn antennas provide superb impulse response & bandwidth (200-1200 MHz)

• Interferometry & beam gradiometry from multiple overlapped antenna measurements

A radio “feedhorn array” for the Antarctica Continent

~320ps Measured

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Major Hurdles • No commercial waveform recorder solution (power/resolution)

• 3σ thermal noise fluctuations occur at MHz rates (need ~2.3σ)

• Without being able to record or trigger efficiently, there is no experiment

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Strategy: Divide and Conquer

• Split signal: 1 path to trigger, 1 for digitizer • Digitizer runs ONLY when triggered to save power

Three key technologies:

1. Very low-noise (low power) amplifiers 2. Efficient, thermal-noise limited triggering 3. Low power, Gsa/s waveform sampling

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Switched Capacitor Array Sampling

Input

Channel 1

Channel 2 Few 100ps delay

• Write pointer is ~4-6 switches closed @ once

20fF

Tiny charge: 1mV ~ 100e-

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Example: LABRADOR performance (similar to other ASICs)

• Excellent linearity, noise • Sampling rates up to 4 GSa/s with voltage overdrive

2.6GSa/s

12-bit ADC

• 10 real bits (1.3V/1.3mV noise)

1.3mV

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A solar powered, airborne HEP experiment

Raw Signals

80 RF channels @ 1.5By * 2.6GSa/s

= 312 Gbytes/s

Level-1

Antenna

3-of-8

100-200kHz @ 36kBy/evt

= 3.6-7.2Gby/s

Level-2

Cluster

2-of-5

Few kHz @ 36kBy/evt = 36-72Mby/s

Level-3 Phi

2-of-2

5-10Hz @ 36kBy/evt

= 180-360kBy/s To disk

Prioritizer (+compress)

Few

eve

nts/

min

TD

RSS

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After full calibration – 100’s km downrange

<30ps timing

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A. Vieregg

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Warning!!! Log Plot!

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ANITA3 – the “last” round

• Rebuild “space flight” readout instrumentation (half a decade old technology) • Threshold limited – new trigger ASIC (RITC) • New digitizer (LAB4) to go to longer waveforms • “going for broke” – ARA is successor

For December 2014 Flight New SURF & TURF

RITC LAB4 25

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How to “go big” ?

• Salt – Salt domes

• Ice – In situ (RICE AURA IceRayARA/ARIANNA) – Overflight (satellite) [high threshold]

• Silica sand – Lunar regolith (GLUE) [high threshold]

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Askaryan Radio Array (ARA)

• Gusev and Zheleznykh proposed in 1983! • 100’s of km3 volume at GZK nu range • Inexpense extention to IceCube

Physics Goals

ARA Readout Electronics (similar to ARIANNA)

• Uplink bandwidth (~1Mbit/s [wireless]) – First (test station) this season

– 1 detector station each of next 2 seasons after (building more) 28

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Askaryan Radio Array

• ANITA trigger/digitizer electronics to ARA • “array crossing” waveform sampler (IRS) • Built “testbed” in mid-2000’s …. • Finally deployed in January 2011, taking data • First “station” January 2012

Development Milestones IRS, IRS2, IRS3 ASIC

ARA Test Bed

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Neutrino Flavor/Current ID

• Charged/neutral current & flavor ID possible on subset of SalSA events • At least 20% of GZK CC events will get first order flavor ID • Detailed initial studies – looks very promising [BLAB ASIC – 64us deep

version of LABRADOR makes possible [NIM A591 (2008) 534]

Charged current (SM: 80%)

Neutral current (SM: 20%)

e 25% hadronic + 75% EM shower at primary vertex; LPM on EM shower

Single hadronic shower at vertex

µ 25% hadronic at primary, 2ndary lepton showers, mainly EM

Single hadronic shower at vertex

τ 25% hadronic at vertex, 2ndary lepton showers, mainly hadronic

Single hadronic shower at vertex

~2 km

1018 eV νµ

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Directions for future ASIC R&D • Low noise amplifiers

– Lower noise figure, lower power

• Better triggering – Only a couple bits needed – Real-time noise correlator

• Deeper waveform sampling – Already at ~100us analog storage – Higher frequency?

• Lower power! – Solar, wind, ??? – Autonomous, robust comm links – Design for manufacture**

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Why nattering on about power?!?

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“Obs Cosmo” Summary

ASICs as the way Forward: • Further discoveries will depend upon evolutionary improvements in the basic instrumentation, of which ASICs play a crucial role

• Interesting problems with much overlap in other disciplines (low noise, high speed, low power)

• “Funding problems” are often mass manufacturing or operations cost issues – room for further ‘enabling technologies’

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Back-up slides

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A great idea that took a while to catch on

– 1962: G. Askaryan predicts coherent radio Cherenkov from particle showers in solid dielectrics – His applications? Ultra-high energy cosmic rays &

neutrinos

– Mid-60’s: Jelley & collaborators see radio impulses from high energy cosmic ray air showers – -- from geo-sychrotron emission, NOT radio

Cherenkov – Renewed interest: LOPES/Codelema

– 1970-2000: Askaryan’s hypothesis

remained unconfirmed – 2000-2001: Argonne & SLAC beamtests

confirm strong radio Cherenkov from showers in silica sand

– Salt (2004) & ice (2006) also tested, all confirmed

Saltzberg, et al PRL 2001

Gorham, et al PRD 2004

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Particle Physics: Energy Frontier

• GZK ν spectrum is an energy-frontier beam: – up to 300 TeV center of

momentum particle physics

– Search for large extra dimensions and micro-black-hole production at scales beyond reach of LHC

� ν Lorentz factors of γ=1018-21

Std. model

Large extra dimensions

Anchordoqui et al. Astro-ph/0307228

GZK ν

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Particle Physics: Neutrinos • GZK neutrinos are the

“longest baseline” neutrino experiment: – Longest L/E (proper time) for:

sterile ν admixtures & anomalous ν decays

• SUN: L/E ~ 30 m/eV • GZK: L/E ~ 109 m/eV

• Measured flavor ratios of νe:νµ:ντ can identify non-standard physics at source

νe:νµ:ντ

(1:1:1)! (5-6):1:1

Neutrino decay leaves a strong imprint on flavor ratios at Earth

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Differential GPS Antennas

Solar cells for NASA equipment

32 Quad-ridge horn antennas - 200 MHz to 1200 MHz - 10 degree downward angle

8 low gain antennas to monitor payload-generated noise

ANITA electronics box

Solar panels for science mission

Battery box

ANITA-1 pieces

“instrument paper” arXiv:0812.1920 [astro-ph]

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9 x 260 samples = 2340 storage cells

Convert all 2340 samples in parallel,

transfer out on common 12-bit data bus

256 + 4 “tail” samples

G. Varner -- Challenges in Radio Detection, Detector R&D WS @ FNAL 40

Large Analog Bandwidth Recorder and Digitizer with Ordered Readout [LABRADOR]

8+1 chan. * 256+4 samples

Straight Shot

RF inputs

Random access:

• Common STOP acquisition

• 3.2 x 2.9 mm • Conversion in

31µs (all 2340 samples)

• Data transfer takes 80µs

• Ready for next event in <150µs

• Switched Capacitor Array (SCA)

• Massively parallel ADC array

• Similar to other WFS ASICs analog bandwidth

NIM A583:447-460, 2007

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Bandwidth Evaluation

Transient Impulse

FFT Difference

Frequency [GHz]

f3dB ~ 1GHz

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Sampling Unit for RF (SURF) board

G. Varner -- Challenges in Radio Detection, Detector R&D WS @ FNAL 43

SURFv3 Board

Trigger Inputs

Programming/ Monitor Header

RF Inputs

LAB3

J4 to TURF J1 to CPU

(SURF = Sampling Unit for RF) (TURF = Trigger Unit for RF)

Flies in space – all components heat sunk

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Quiet, but are we sensitive?

Ground pulser

Dipole

Bore hole pulser

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Validation data: borehole pulser

• RF Impulses from borehole antenna at Williams field

• Detected at payload out to 300-400 km, consistent with expected sensitivity

• Allows trigger & pointing calibration

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S. Hoover

Askaryan Radio Array (ARA)

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Cluster Station

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